Himmelsbach et al in CA 2,054,850 discuss aggregation inhibiting compounds of the formula: EQU B--X--A--Y--E
wherein A may be a cyclic imino such as pyrrolidine and amidst the various definitions of B and X one can find amidino and arylene listed. The combination of Y--E, however, is not considered to be useful for the present invention. Thus, the compounds of Himmelsbach et al differ from those of the present invention. Moreover, inhibition of factor Xa is not discussed in Himmelsbach et al as a use for the compounds of the above formula.
In U.S. Pat. No. 5,463,071, Himmelsbach et al depict cell aggregation inhibitors which are 5-membered heterocycles of the formula: ##STR2## wherein the heterocycle is other than pyrroline and pyrrolidine and groups A--B--C-- and F--E--D-- are attached to the ring system. A--B--C-- can be a wide variety of substituents including a basic group attached to an aromatic ring. The F--E--D-- group, however, would appear to be an acidic functionality which differs from the present invention. Furthermore, use of these compounds as inhibitors of factor Xa is not discussed.
Activated factor Xa, whose major practical role is the generation of thrombin by the limited proteolysis of prothrombin, holds a central position that links the intrinsic and extrinsic activation mechanisms in the final common pathway of blood coagulation. The generation of thrombin, the final serine protease in the pathway to generate a fibrin clot, from its precursor is amplified by formation of prothrombinase complex (factor Xa, factor V, Ca.sup.2+ and phospholipid). Since it is calculated that one molecule of factor Xa can generate 138 molecules of thrombin (Elodi, S., Varadi, K.: Optimization of conditions for the catalytic effect of the factor IXa-factor VIII Complex: Probable role of the complex in the amplification of blood coagulation. Thromb. Res. 1979, 15, 617-629), inhibition of factor Xa may be more efficient than inactivation of thrombin in interrupting the blood coagulation system.
Therefore, efficacious and specific inhibitors of factor Xa are needed as potentially valuable therapeutic agents for the treatment of thromboembolic disorders. It is thus desirable to discover new factor Xa inhibitors.